The present invention relates to a low insertion force terminal, and in particular relates to a terminal used in a surface mounted, high density electrical connector called a BGA connector (Ball Grid Array connector) that is connected to a substrate via a solder ball.
Parallel with the increasing density and reduction in size of electrical apparatuses such as computers, the development of BGA connectors that can reduce the mounting surface area is making progress. The BGA connector is a connector whose form has a plurality of terminals accommodated within the housing respectively connected to each of a plurality of exposed solder balls arranged in a array on one surface of a housing comprising an insulating material. When the BGA connector is mounted on a substrate, solder balls are placed in contact with a plurality of contact pads arranged on the substrate in the same manner and baked. During baking, a portion of each solder ball melts, and the terminal and contact pad are bonded via the solder ball. With this type of BGA connector, because the gap between adjacent solder balls can be extremely narrow, there are the advantages that the mounting surface area on the substrate is small, and extensive wiring can be implemented.
The structure disclosed, for example, in the Specification of U.S. Pat. No. 5,092,789, is a terminal used in this type of connector that has the terminals arranged in such an array. As shown in FIG. 3, the terminal 1 used in this connector comprises a female terminal 2 accommodated in a housing of the contact (not illustrated) and a male terminal 3 anchored to a lid member (not illustrated).
This male terminal 3 is formed into a round rod shape projecting in a vertically downward direction from the lid member. The female terminal 2 possesses a bottom part (not illustrated) through which a connection part (not illustrated) for connecting to the substrate projects from the bottom surface of the housing and a pair of upright parts 4, 5 extending in a cantilever beam shape upwards from this bottom part. On the upper ends of these upright parts 4, 5, opposing male terminal grasping parts 4a, 5a, are formed separated by a gap smaller than the diameter of the male terminal 3. When the male terminal 3 is inserted by pressing, the dimensions of the gap between these male connector grasping parts 4a, 5a expand, and due to the flexible restoring force of the upright parts 4, 5, the male terminal 3 can be supported in a grasped state.
In order to simplify the insertion of the male terminal 3 into the male support parts 4a, 5a, on one side in the widthwise direction of the male terminal support parts 4a, 5a, a guide part 6 is formed that has a pair of opposing out-turned surfaces 4b, 5b separated by a gap therebetween gradually widening in the widthwise direction from the male terminal support parts 4a, 5a. Therefore, when the male terminal 3 is inserted into the female terminal 2, the male terminal 3 must be pressed against each out-turned surface 4b, 5b of this guide part 6 and inserted while widening the gap between the male terminal support parts 4a, 5a. 
However, with the terminal 1 having this kind of structure, when the gap between the male terminal support parts 4a, 5a is pushed open by the male terminal 3, a force that pushes the male terminal 3 forward while overcoming the frictional force from the pair of out-tuned surfaces 4b, 5b in the guide part 6 of the female terminal 2, and a force acting on to the pair of out-turned surfaces 4b, 5b in order to flexibly deform the upright parts 4, 5 of the female terminal 2 must be applied simultaneously. Due to this, the peak value of the insertion force applied to the male terminal 3 is extremely high. Furthermore, when male terminals 3 and female terminals 2 a re connected simultaneously in a plurality of terminals 1 as in the case of a BGA connector, the insertion force that must be applied simultaneously to all terminals 1 becomes excessive. Depending on the case, carrying out the connection operation manually is difficult, and as disclosed in the Specification of U.S. Pat. No. 5,092,789, a handle for carrying out the connection operation must be provided.
In consideration of the above-described problems, an object of the present invention is to provide a low insertion force terminal comprising a female terminal and a male terminal, said female terminal being characterized in providing a bottom soldered to wiring and a pair of facing upright parts extending from said bottom in a cantilever beam shape; and wherein an extended part is provided that projects in the widthwise direction on the distal end of one of said upright parts farther than the distal end part of the other upright part, and a male terminal supporting part that grasps and supports the male terminal is provided at a position in proximity to said extended part of said pair of upright parts.
In the above-described low insertion force terminal, the extended part is formed so as to capable of being pressed by said male part, and at the same time the contact surface with the male part from said extended part to said male terminal support part is flattened in the widthwise direction of said upright part.
Furthermore, in the above-described low insertion force terminal, the contact surface with the male terminal from the extended part to the male terminal support part is formed so as to curve in the lengthwise direction of the upright part such that a convex surface is imparted.
According to the low insertion force terminal of the present invention, when a male terminal and a female terminal are connected, the extended part formed at the distal end of one of the upright parts is pressed. Thereby, the distal end of this one upright part is separated from the distal end of the other upright part, and an insertion space for the male terminal can be maintained. In this state the male terminal is moved in the widthwise direction of the upright parts of the female terminal, and after being moved up to the male terminal support part in proximity to the extended part, the pressing force applied to the extended part is released, and thereby the male terminal is grasped within the male terminal support part of the female terminal, and both terminals become electrically and mechanically connected.
In this case, because the male terminal is inserted between the upright parts after carrying out the separation operation of the upright parts of the female terminal separately from the insertion operation of the male terminal, the male terminal and female terminal can be connected without excessive insertion force.
Furthermore, because the extended part can be pushed by the male terminal and the contact surface with the male terminal from this extended part to the male terminal supporting part is flattened in the widthwise direction of the upright parts, in the state wherein the pair of upright parts are separated, simply by moving the male terminal along the widthwise direction of the upright parts, the male terminal can be moved from the extended part to the male terminal support part without fluctuation of the frictional force. That is, since there is no peak value for the frictional force, the insertion force can be decreased.
In addition, because the contact surface with the male terminal from the extended part to the male terminal support part is formed by curving the upright part in the lengthwise direction so as to impart a convex surface, the contact surface area with the male terminal is decreased, and the frictional force generated while the male terminal moves to the male terminal support part can be decreased.